Bug#955997: rust-libc: autopkgtest failure.

[peter green]

Version: 0.2.68-2

The autopkgtest is now passing.

https://ci.debian.net/data/autopkgtest/testing/amd64/r/rust-libc/4955258/log.gz

(that is an unstable to testing migration test, but I'd be surprised if the 
plain unstable test was different).